package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Slf4j
@Component
public class CacheClient {
    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }
    public void set (String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);
    }

    public void setWithLogicalExpire (String key,Object value,Long time,TimeUnit unit){
        RedisData redisData=new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //redis
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(redisData));
    }

    public <R,ID> R queryWithPassThrough(
            String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback,Long time,TimeUnit unit){
        String key=keyPrefix+id;
        //1.从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isNotBlank(json)){
            //3.存在，直接返回

            return JSONUtil.toBean(json, type);
        }
        //命中的是否是空值
        if (json != null) {
            return null;
        }
        //4.不存在。根据id查询数据库

        R r = dbFallback.apply(id);
        //5.数据库也不存在返回错误
        if (r == null) {
            //空值写入redis
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        //6.存在写入redis
        this.set(key,r,time,unit);
          //7.返回
        return r;
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR= Executors.newFixedThreadPool(10);

    public <R,ID> R queryWithLogicalExpire(String keyPrefix ,ID id,Class<R> type,Function<ID,R> dbFallback,Long time,TimeUnit unit){
        String key=keyPrefix+id;
        //1.从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if(StrUtil.isBlank(json)){
            //3.不存在，直接返回
            return null;
        }
        //4.命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())){
            //5.1未过期，直接返回店铺信息
            return r;
        }
        //5.2已过期需要缓存重建
        //6.缓存重建
        //6.1 获取互斥锁
        String lockKey=LOCK_SHOP_KEY+id;
        boolean isLock=tryLock(lockKey);
        //6.2判断是否获取锁成功
        if(isLock){
            //6.3成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() ->{
                try {
                    R r1 = dbFallback.apply(id);
                    this.setWithLogicalExpire(key,r1,time,unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    unLock(lockKey);
                }
            });

        }
        //6.4返回过期的商铺信息
        return r;
    }

    private boolean tryLock (String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unLock(String key){
        stringRedisTemplate.delete(key);
    }

}
